One of the major inconveniences and sources of expense in the operation of shaft furnaces has been the need to replace the refractory lining of the furnace at intervals. By cooling the refractory lining it can be made to last longer, but the replacement of the cooling means increases the complexity and expense of the relining operation. A method of cooling shaft furnaces known as stave cooling has been known for over fifty years and has generally found favor. This method involves the provision of cast-iron staves or blocks fixed to the furnace shell and in contact with the refractory lining of the furnace. The staves support water-carrying pipes running through them parallel, either vertically or horizontally, to the walls of the furnace and these pipes are disposed at varying distances from the hottest surface of the stave. The disposition of the pipes is such that as one pipe fails as a result of the wear on the stave other pipes situated further from the hottest surface are still operating and take over as the cooling element at the hottest part of the stave.
The cooling system outlined above presents several difficulties, the main ones of which are as follows. It is difficult to cast the pipes in the stave because the pipes tend to become carbonised and hence brittle and may then crack under stress. If, as is usual, the pipes are insulated to avoid becoming carbonised heat transfer between the stave and the water in the pipes is reduced. Each pipe is required to have its own inlet and outlet, and with the commonly used system of four pipes in each stave considerable piping costs are incurred. Once the furthest pipe has been rendered inoperative by the wearing away of the stave the only way in which the furnace can be cooled is to turn the water supply off where it is applied to the pipe inlets and allow the water to flow down the furnace shell. This type of external cooling is not very effective.